Phosphorus element-containing crosslinking agents and flame retardant phosphorus element-containing epoxy resin compositions prepared therewith

ABSTRACT

A flame retardant phosphorus element-containing epoxy resin composition substantially free of halogen, including:  
     (I) a non-halogenated epoxy resin material selected from:  
     (A) a non-halogenated phosphorus element-containing epoxy resin;  
     (B) a mixture of:  
     (1) a non-halogenated, non-phosphorus element-containing epoxy resin, and  
     (2) a phosphorus element-containing compound; or  
     (C) the reaction product of:  
     (1) a non-halogenated epoxy resin; and  
     (2) a phosphorus element-containing compound; or  
     (D) a combination of two or more of components (A) to (C); and  
     (II) (A) a multi-functional phenolic crosslinking agent having a hydroxy functionality of at least 2; (B) a material which forms a multifunctional phenolic crosslinking agent having a hydroxy functionality of at least 2, upon heating or (C) a mixture of components (A) and (B); in an amount of from about 50% to about 150% of the stoichiometric amount needed to cure the epoxy resin. Electrical laminate circuit boards having reduced flammability may be made from these compositions.

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/170,421, filed Dec. 13, 1999.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to curable phosphoruselement-containing epoxy resin formulations, and particularly toformulations useful for making laminates for printed wiring boards andcomposite materials.

[0003] It is known to make electrical laminates and other compositesfrom a fibrous reinforcement and an epoxy-containing matrix resin.Examples of suitable processes usually contain the following steps:

[0004] (1) an epoxy-containing formulation is applied to or impregnatedinto a substrate by rolling, dipping, spraying, other known techniquesand/or combinations thereof. The substrate is typically a woven ornonwoven fiber mat containing, for instance, glass fibers or paper.

[0005] (2) The impregnated substrate is “B-staged” by heating at atemperature sufficient to draw off solvent in the epoxy formulation andoptionally to partially cure the epoxy formulation, so that theimpregnated substrate can be handled easily. The “B-staging” step isusually carried out at a temperature of from 90° C. to 210° C. and for atime of from 1 minute to 15 minutes. The impregnated substrate thatresults from B-staging is called a “prepreg.” The temperature is mostcommonly 100° C. for composites and 130° C. to 200° C. for electricallaminates.

[0006] (3) One or more sheets of prepreg are stacked or laid up inalternating layers with one or more sheets of a conductive material,such as copper foil, if an electrical laminate is desired.

[0007] (4) The laid-up sheets are pressed at high temperature andpressure for a time sufficient to cure the resin and form a laminate.The temperature of this lamination step is usually between 100° C. and230° C., and is most often between 165° C. and 190° C. The laminationstep may also be carried out in two or more stages, such as a firststage between 100° C. and 150° C. and a second stage at between 165° C.and 190° C. The pressure is usually between 50 N/cm² and 500 N/cm². Thelamination step is usually carried out for a time of from 1 minute to200 minutes, and most often for 45 minutes to 90 minutes. The laminationstep may optionally be carried out at higher temperatures for shortertimes (such as in continuous lamination processes) or for longer timesat lower temperatures (such as in low energy press processes).

[0008] (5) Optionally, the resulting laminate, for example, acopper-clad laminate, may be post-treated by heating for a time at hightemperature and ambient pressure. The temperature of post-treatment isusually between 120° C. and 250° C. The post-treatment time usually isbetween 30 minutes and 12 hours.

[0009] It is conventional in the preparation of epoxy-containinglaminates to incorporate into the epoxy resin composition variousadditives to improve the flame-retardancy of the resulting laminate.Many types of flame retardant additives have been suggested, but theadditives which are most widely used commercially are halogen-containingadditives, such as tetrabromodiphenylolpropane, or epoxy resins preparedby reacting diglycidyl ether of bisphenol-A withtetrabromodiphenylolpropane. Typically, in order to reach the desiredfire retardancy level (V-0 in the standard “Underwriters Laboratory”test method UL 94), levels of such bromine-containing flame retardantadditives are required which provide a bromine content of from 10 wt %to 25 wt % based on the total polymer weight in the product.

[0010] Although halogen-containing fire-retardant additives such astetrabromodiphenylolpropane, are effective, they are considered by someto be undesirable from an environmental standpoint, and in recent yearsthere has been increasing interest in the formulation of halogen-freeepoxy resins, which are able to meet the fire retardancy requirements.

[0011] Proposals have been made to use phosphorus-based flame retardantsinstead of halogenated fire retardants in epoxy resin formulations asdescribed in, for example, EP A 0384939, EP A 0384940, EP A 0408990, DEA 4308184, DE A 4308185, DE A 4308187, WO A 96/07685, and WO A 96/07686.In these formulations a phosphorus flame retardant is pre-reacted withan epoxy resin to form a di- or multifunctional epoxy resin which isthen cured with an amino cross-linker such as dicyandiamide,sulfanilamide, or some other nitrogen element-containing cross-linker toform a network.

[0012] There are some commercially available phosphorus-based fireretardant additives which may be useful for replacing halogen-containingfire-retardant additives. For example, Amgard™ V19 and Antiblaze™ 1045(previously Arngard™ P45) supplied by Albright and Wilson Ltd, UnitedKingdom, are commercially available phosphonic acid ester fire retardantmaterials. These phosphonic acid esters, may be solids or liquids.

[0013] Alkyl and aryl substituted phosphonic acid esters are compatiblewith epoxy resins. In particular, lower alkyl (i.e., C₁-C₄) esters ofphosphonic acid are of value because they contain a high proportion ofphosphorus, and are thus able to impart good fire retardant propertiesupon resins in which they are incorporated. However, the phosphonic acidesters are not satisfactory as a substitute for halogenated flameretardants in epoxy resins for the production of electrical laminates,because the use of phosphonic acid esters, used in amounts sufficient toprovide the necessary flame retardancy, increases the tendency of theresulting cured epoxy resin to absorb moisture. The moisture absorbencyof a cured laminate board is very significant, because laminatescontaining high levels of moisture tend to blister and fail, whenintroduced to a bath of liquid solder at temperatures around 260° C., atypical step in the manufacture of printed wiring boards.

[0014] Another system, which utilizes a phosphorus-based flameretardant, is described in EP A 0754728. EP A 0754728 describes theproduction of flame retardant epoxy resin systems by blending epoxyresins with a cyclic phosphonate as a flame retardant and incorporatingthe cyclic phosphonate into the cured resin. The epoxide resin andphosphonate mixture is crosslinked with a polyamine such astriethylamine, tetra amine, polyamido amines, multi basic acids or theiranhydrides for example phthalic anhydride or hexahydrophthalicanhydride. EP A 0754728 indicates that large quantities, such as inexcess of 18 wt %, of the phosphorus additive are needed in order forthe resin system to meet UL 94 V-0.

[0015] WO 99/00451 also discloses flame retardant epoxy resincompositions utilizing phosphonic acid esters. WO 99/00451 discloses thereaction of a phosphonic acid ester with an epoxy resin in the presenceof a catalyst and a nitrogen-containing crosslinking agent. Thecrosslinking agent has an amine functionality of at least 2 and ispreferably dicyandiamide. The epoxy resins described in WO 99/00451 haveimproved flame retardant properties at low levels of phosphonic acidester flame retardant. However, there is still a need in the industryfor a flame retardant epoxy resin composition with improved Tg and flameretardancy.

SUMMARY OF THE INVENTION

[0016] The present invention is directed to epoxy resins which meet thedesirable standards of fire retardancy without the need forhalogen-containing flame retardants. The epoxy resin compositions of thepresent invention employ relatively low levels of a phosphoruselement-containing compound in the resin (for example, to provide fromabout 0.2 wt % to about 3.5 wt % phosphorus in a solid resin or a solidcuring formulation), together with particular combinations of amulti-functional phenolic hardener, an accelerator and a catalyst, and,in preferred embodiments, particular types of epoxy resins. Themulti-functional phenolic hardeners, accelerators and catalysts aregenerally known per se, but their use in conjunction with low levels offire retardants to obtain compositions which have both good fireretardancy, and yet sufficiently low water absorption has not hithertobeen described.

[0017] According to one aspect of present invention, there is provided aflame retardant curable phosphorus element-containing epoxy resincomposition substantially free of halogen, comprising:

[0018] (I) a non-halogenated epoxy resin material selected from:

[0019] (A) a non-halogenated phosphorus element-containing epoxy resin;

[0020] (B) a mixture of:

[0021] (1) a non-halogenated, non-phosphorus element-containing epoxyresin, and

[0022] (2) a phosphorus element-containing compound; or

[0023] (C) the reaction product of:

[0024] (1) a non-halogenated epoxy resin; and

[0025] (2) a phosphorus element-containing compound; or

[0026] (D) a combination of two or more components (A) to (C);

[0027] (II) (A) a multi-functional phenolic crosslinking agent having ahydroxy functionality of at least 2;

[0028] (B) a material which forms a multi-functional phenoliccross-linking agent having a hydroxy functionality of at least 2 uponheating; preferably in amount of from about 50% to about 150% of thestoichiometric amount needed to cure the epoxy resin; or

[0029] (C) a mixture of components (A) and (B); and

[0030] (III) optionally, a catalyst capable of promoting the reaction ofthe phenolic/hydroxy group of the multi-functional phenolic crosslinkingagent with the epoxy group of the epoxy resin material.

[0031] Another aspect of present invention is directed to providing aflame retardant hardener composition substantially free of halogen,comprising:

[0032] (a) (i) a multi-functional phenolic crosslinking agent having ahydroxy functionally of at least 2 or (ii) a material which forms amulti-functional phenolic cross-linking agent having a hydroxyfunctionality of at least 2 upon heating or (iii) a mixture ofcomponents (i) and (ii); preferably in an amount of from about 50% to150% of the stoichiometric amount needed to cure an epoxy resin;

[0033] (b) a phosphorus element-containing compound; the phosphoruselement-containing compound preferably having an amine, a phosphine, aphosphate, a hydroxy, an anhydride, or an acid functionality, andpreferably, in an amount such as to provide from about 0.2 wt % to about3.5 wt % phosphorus in a final curing formulation composition; and

[0034] (c) optionally, a Lewis acid inhibitor.

[0035] A preferred embodiment of the present invention includes an epoxyresin having a reduced number of aliphatic chain groups in the curedepoxy resin composites network. The lower number of aliphatic chaingroups is believed to reduce the methane gas emissions during burning.

[0036] It has also been found that the reaction product or epoxy adductproduced by reacting a non-halogenated epoxy resin and a phosphoruselement-containing compound surprisingly provides advantageous benefitswhen used for preparing the flame retardant formulations of the presentinvention. Accordingly, another aspect of the present invention isdirected to a phosphorus element-containing epoxy resin adductcomprising the reaction product of (1) a non-halogenated epoxy resin;and (2) a phosphorus element-containing compound which is preferably achain extender which has a functionality of from about 1 to about 3,more preferably from about 1.8 to about 2.2. The chain extender may befor example a hydroxy functional or an amine functional compound such asfor example 10-(2′,5′-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] In its broadest scope, the present invention is a flame retardantepoxy resin composition substantially free of halogen including: (I) anon-halogenated epoxy resin material with some specific amount ofphosphorus element therein; and (II) a multi-functional phenoliccrosslinking agent having a hydroxy functionality of at least 2. A resinwhich is “substantially free of halogen” means that the resin iscompletely free of halogen, i.e. 0% halogen, or that the resin containssome minor amount of halogen that does not affect the properties orperformance of the resin, and is not detrimental to the resin.“Substantially free of halogen”, therefore, herein includes for example,wherein the resin contains up to about 10 weight percent halogen, butpreferably contains less than about 10 weight percent, more preferablyless than about 5 weight percent, even more preferably less than about 1weight percent and most preferably zero weight percent of a halogen inthe resin composition.

[0038] In order to obtain satisfactory flame retardancy and stillprovide the benefit of resistance to water absorption, it is importantthat the amount of the phosphorus element in the resin composition isfrom about 0.2 wt % to about 3.5 wt %, preferably from about 1 wt % toabout 3 wt %, more preferably from about 1.5 wt % to about 2.8 wt %,based on the total amount of the solid curing resin composition.

[0039] The multi-functional phenolic cross-linker (II) of the presentinvention, also referred to interchangeably herein as a hardener orcuring agent, preferably contains at least two or more functionalities.The crosslinker (II) may be selected from (A) a phenolic crosslinkingagent having a functionality of at least 2; (B) a material or compoundwhich forms a phenolic crosslinking agent having a functionality of atleast 2, upon heating or (C) a mixture of components (A) and (B). Thephenolic hardeners (II) are compounds, either polymeric or monomeric,which have at least 2 phenolic —OH (hydroxyl groups) capable of reactingwith epoxy groups at elevated temperatures. The phenolic hardenersinclude various types of compounds such as:

[0040] a. Phenolic resins obtained from phenols or alkyl phenols andformaldehyde, such as phenol novolacs or resoles, as described in Lee &Neville, section 11-14;

[0041] b. 3,4,5-trihydroxybenzoic acid (also known as gallic acid) orits derivatives, or pyrogallol (also known as 1,2,3-trihydroxybenzol),or 1,2,4-trihydroxybenzol (also known as hydroxyhydrochinon);

[0042] c. 1,8,9-trihydroxyanthracene(also known as dithranol or1,8,9-anthracentriol), or 1,2,10-trihydroxyanthracene (also known asanthrarobine);

[0043] d. 2,4,5-trihydroxypyrimidine;

[0044] e. tris(hydroxyphenyl)methane;

[0045] f. dicylcopentadiene phenol novolac;

[0046] g. tetraphenolethane; and

[0047] h. copolymer of styrene and hydroxystyrene.

[0048] The chemical structure of some of the phenolic hardeners (II)described above are as follows:

[0049] The multi-functional phenolic cross-linker (II) is preferably anovolac or a cresol novolac obtained by the condensation of phenols,cresols, xylenols or other alkyl phenols with a formaldehyde. Also, inthe present invention, the resoles may be used as the multi-functionalphenolic cross-linker.

[0050] Preferably, the multi-functional phenolic cross-linker (II) ofthe present invention has the following chemical structural formula:

[0051] wherein “R” is hydrogen or a C₁-C₃ alkyl, e.g., methyl; and “n”is 0 or an integer from 1 to 10. “n” preferably has an average value offrom 0 to 5. The preferred crosslinker (II) is when R is preferably ahydrogen in the above Formula I.

[0052] Commercially available products having the above general FormulaI for the crosslinking agent (II) include for example, Perstorp 85.36.28which is a phenolic resin obtained from phenol and formaldehyde havingan average Mettler softening point of 103° C., melt viscosity at 150°C.=1.2 Pa.s and a functionality of 4 to 5. Another example includesDurite SD 1731 from Borden Chemical of U.S.A.

[0053] Examples of compounds (B) which form a phenolic crosslinkingagent (II) upon heating include phenolic species obtained from heatingbenzoxazine, for example as illustrated in the following chemicalequation:

[0054] wherein n is greater than 1; and wherein R′ and R″ may be,independently and separately, the same or different hydrogen, an allylgroup from C₁- C₁₀ such as methyl, a C₆-C₂₀ aromatic group such asphenyl or a C₄-C₂₀ cycloaliphatic group such as cyclohexane.

[0055] Examples of compounds (B) also include benzoxazine ofphenolphthalein, benzoxazine of bisphenol-A, benzoxazine of bisphenol-F,benzoxazine of phenol novolac and the like. Mixtures of components (A)and (B) described above may also be used.

[0056] The multi-functional phenolic cross-linker (II) is preferablyused in the epoxy resin composition in an amount of from about 50% toabout 150% of the stoichiometric amount needed to cure the epoxy resinand more preferably from about 75% to about 125% of the stoichiometricamount needed to cure the epoxy resin, even more preferably from about85% to about 110% of the stoichiometric amount needed to cure the epoxyresin.

[0057] Optionally, other co-cross-linking agents (VII) may be used incombination with the multi-functional phenolic cross-linking agent.Suitable multifunctional co-cross-linkers useful in the presentinvention are described in numerous references such as Vol. 6Encyclopedia of Poly. Sci. & Eng., “Epoxy Resins” at 348-56 (J. Wiley &Sons 1986).

[0058] Some of the co-cross-linkers (VII) useful in the presentinvention include, for example, anhydrides such as a carboxylic acidanhydrides, styrene maleic anhydride copolymers, maleic anhydrideadducts of methylcyclopentadiene and the like; amino compounds such asdicydiamide, sulfanilamide, 2,4-diamino-6-phenyl-1,3,5 triazine, and thelike; carboxylic acids such as salicylic acid, phthalic acid and thelike; cyanate esters such as dicyanate of dicyclopentadienyl bisphenol,dicyanate of bisphenol-A and the like; isocyanates such as MDI, TDI andthe like; and bismaleic triazines and the like.

[0059] In one preferred embodiment, for example, a nitrogen-containingcross-linker (VII) can be used as a subsidiary or co-cross-linker inaddition to the multi-functional phenolic cross-linker (II). Thenitrogen-containing co-cross-linking agent has an amine functionality ofat least 2. Examples of suitable nitrogen-containing cross-linkersuseful in the present invention may be found in WO 99/00451,incorporated herein by reference; and include for example, polyamines,polyamides, sulfanilamide, diaminodiphenylsulfone and diaminodiphenylmethane and dicyandiamide, substituted dicyandiamide,2,4-diamino-6-phenyl-1,3,5-triazine. When a nitrogen-containingcross-linker is used in the present formulation, the preferrednitrogen-containing cross-linkers are dicyandiamide, sulfanilamide and2,4-diamino-6-phenyl-1,3,5-triazine, more preferably sulfanilamide isused.

[0060] Another preferred embodiment of co-crosslinkers (VII) useful inthe present invention are described in U.S. patent application Ser. No.09/008983, entitled “Latent Catalysts for Epoxy Curing Systems” filedJan. 20, 1998, by Gan et al.; which is incorporated herein by reference;and include for example copolymers of styrene and maleic anhydridehaving a molecular weight (M_(w)) in the range of from 1500 to 50,000and an anhydride content of more than 15 percent. Commercial examples ofthese materials include SMA 1000, SMA 2000, and SMA 3000 havingstyrene-maleic anhydride ratios of 1:1, 2:1, and 3:1 respectively andhaving molecular weights ranging from 6,000 to 15,000; and which areavailable from Elf Atochem S.A.

[0061] When a co-crosslinker is used in the present invention, theco-crosslinker is present in an amount to crosslink less than 40% ofstoichiometric amount needed to cure the epoxy resin. Preferably, theamount of the crosslinking agent in the epoxy resin is from 0 to 40% ofthe stoichiometric quantity needed to cure the epoxy content of theepoxy resin in the formulation.

[0062] The non-halogenated epoxy resin material (I) used in the presentinvention generally contains a phosphorus element or introduces aphosphorus element into the resin composition of the present invention.Generally, the epoxy resin material (I) is used in an amount of fromabout 30 wt % to about 95 wt %. The non-halogenated epoxy resin materialcomponent (I) may be selected from: (A) a non-halogenated phosphoruselement-containing epoxy resin; or (B) a mixture of: (1) anon-halogenated, non-phosphorus element-containing epoxy resin, and (2)a phosphorus element-containing compound which can be either reactivewith or non-reactive with the epoxy resin (B1); (C) the reaction productof: (1) a non-halogenated epoxy resin which can be either aphosphorous-element containing epoxy resin or a non-phosphorous-elementcontaining epoxy resin; and (2) a phosphorus element-containing compoundor (D) a combination of two or more of components (A) to (C).

[0063] Generally, the non-halogenated epoxy resin material (I) used inthe present invention is a material which possesses on average more than1 and preferably at least 1.8, more preferably at least 2 epoxy groupsper molecule. In the broadest aspect of the present invention, the epoxyresin material may be any saturated or unsaturated aliphatic,cycloaliphatic, aromatic or heterocyclic compound which possesses morethan one 1,2-epoxy group.

[0064] In one preferred embodiment, the non-halogenated epoxy resinmaterial (I) is a non-halogenated phosphorus element-containing epoxyresin (A) selected from those described in U.S. Pat. No. 5,376,453,incorporated herein by reference, including for example methyldiglycidyl phosphonate, ethyl diglycidyl phosphonate, propyl diglycidylphosphonate, butyl diglycidyl phosphonate, vinyl diglycidylphosphponate, phenyl digycidyl phosphonate and biphenyl diglycidylphosphonate; methyl diglycidyl phosphate, ethyl diglycidyl phosphate,n-propyl diglycidyl phosphate, n-butyl diglycidyl phosphate, isohbutyldiglycidyl phosphate, allyl diglycidyl phosphate, phenyl diglycidylphosphate, p-methoxyphenyl diglycidyl phosphate, p-ethoxyphenyldiglycidyl phosphate, p-propyloxyphenyl diglycidyl phosphate,p-isopropyloxyphenyl digycidyl phosphate, phenylthiodiglycidylphosphate, triglycidyl phosphate, tris(glycidylethyl) phosphate,p-glycidyl-phenyl ethyl glycidyl phosphate, benzyl diglycidylthiophosphate, and combinations thereof.

[0065] The non-halogenated phosphorus element-containing epoxy resin (A)can also be obtained by either:

[0066] (a) reacting an epoxy resin with a phosphorus element-containingcompound capable of reacting with an epoxy resin; or

[0067] (b) epoxidizing a phosphorus element-containing compound, such asa diol.

[0068] Examples of a non-halogenated phosphorus element-containing epoxyresin (A) useful in the present invention which is obtained by reactingan epoxy resin with a phosphorus element-containing compound capable ofreacting with an epoxy resin include:

[0069] (a) The reaction product of: (i) an epoxy novolac, such asD.E.N.* 438 or D.E.N.* 439 which are trademarks of and commerciallyavailable from The Dow Chemical Company; a trisepoxy such as Tactix 742(Trademark of Ciba Geigy); a dicyclopentadiene phenol epoxy novolac; ora glycidyl of tetraphenolethane and (ii) a phosphorus element-containingcompound reactive with the epoxy resin such as9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, such as “Sanko-HCA”which is commercially available from Sanko of Japan, or “StruktolPolydis PD 3710” which is commercially available from Schill-Seilacherof Germany; or

[0070] (b) the reaction product of: (i) an epoxy novolac, such asD.E.N.* 438 or D.E.N.* 439; a trisepoxy such as Tactix 742; adicyclopentadiene phenol epoxy novolac; a glycidyl of tetraphenolethane;a diglycidyl ether of bisphenol-A; or a diglycidyl ether of bisphenol-Fand (ii) a phosphorus element-containing compound selected from10-(2′,5′dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide,such as “Sanko HCA-HQ” which is commercially available from Sanko ofJapan; bis(4-hydroxyphenyl)phosphine oxide;tris(2-hydroxyphenyl-phosphine oxide;dimethyl-1-bis(4-hydroxyphenyl)-1-phenylmethylphonate; ortris(2-hydroxy-4/5-methylphenyl)phosphine oxide; or

[0071] (c) the reaction product of an epoxy resin and a phosphite; or

[0072] (d) the reaction product of an epoxy resin and a phosphinic acid.

[0073] Examples of a non-halogenated phosphorus element-containing epoxyresin (A) useful in the present invention which is obtained byepoxidizing a phosphorus element-containing compound include: theepoxidized product of a phosphorus element-containing compound such as9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide such as “Sanko-HCA”commercially available from Sanko of Japan or “Struktol Polydis PD 3710”commercially available from Schill-Seilacher of Germany;10-(2′,5′-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (such as “SankoHCA-HQ”); bis(4-hydroxyphenyl)phosphine oxide; tris(2-hydroxyphenyl)phosphine oxide;dimethyl-1-bis(4-hydroxyphenyl)-1-phenylmethylphonate;tris(2-hydroxy-4/5-methylphenyl)phosphine oxidetris(4-hydroxyphenyl)phosphine oxide,bis(2-hydroxyphenyl)phenylphosphine oxide,bis(2-hydroxyphenyl)phenylphosphinate,tris(2-hydroxy-5-methylphenyl)phosphine oxide; or mixtures thereof. Theepoxidizing of the phosphorus element-containing compound is usuallycarried out with an epihalohydrin such as epichlorohydrin well known tothose skilled in the art.

[0074] In still another example of the epoxy resin (A) useful in thepresent invention is an epoxy resin which is the reaction product of anepoxy compound containing at least two epoxy groups and a chain extenderas described in WO 99/00451, incorporated herein by reference. Thepreferred reaction product described in WO 99/00451 useful in thepresent invention is an epoxy-polyisocyanate adduct or anepoxy-terminated polyoxazolidone as described in U.S. Pat. No.5,112,931, incorporated herein by reference. The isocyanate compounds aschain extenders include for example MDI, TDI and isomers thereof.

[0075] In another preferred embodiment, the non-halogenated epoxy resinmaterial (I) used in the present invention is (B) a blend or a mixtureof (1) a non-halogenated, non-phosphorus element-containing epoxy resincompound containing at least two epoxy groups, and (2) a phosphoruselement-containing compound. In other words, it is possible to add thephosphorus element-containing compound (B2) and the epoxy resin compound(B1) mixture to the overall resin composition of the present inventionin order to form a non-halogenated phosphorus element-containing epoxyresin material (I) in-situ.

[0076] The phosphorus element-containing compound or monomer (B2) usefulin the present invention contains some reactive groups such as aphenolic group, an acid group, an amino group, an acid anhydride group,a phosphite group, or a phosphinate group which can react with the epoxygroups of the non-halogenated, non-phosphorus element containing epoxyresin compound (B 1).

[0077] The phosphorus element-containing compound (B2) of the presentinvention may contain on average one or more than one functionalitycapable of reacting with the epoxy groups. Such phosphoruselement-containing compound preferably contains on average 0.8 to 5,more preferably 0.9 to 4, and most preferably 1 to 3 functional groupscapable of reacting with epoxy resin.

[0078] The phosphorus element-containing compounds (B2) useful in thepresent invention include for example one or more of the followingcompounds: P-H functional compounds such as for example HCA,dimethylphosphite, diphenylphosphite, ethylphosphonic acid,diethylphosphinic acid, methyl ethylphosphinic acid, phenyl phosphonicacid, phenyl phosphinic acid, vinyl phosphoric acid, phenolic (HCA-HQ)and the like; tris(4-hydroxyphenyl)phosphine oxide,bis(2-hydroxyphenyl)phenylphosphine oxide,bis(2-hydroxyphenyl)phenylphosphinate,tris(2-hydroxy-5-methylphenyl)phosphine oxide; acid anhydride compoundssuch as M-acid-AH and the like; and amino functional compounds such forexample bis(4-aminophenyl)phenylphosphate, and mixtures thereof. Thechemical structure of some of the compounds (B2) described above are asfollows:

[0079] wherein X is CR₃R₄—(CR₁R₂)_(n)—CR₅R₆ or o-phenylidene, n is 0 or1 and R₁-R₈ may be the same or different and represent H, CH₃, or C₂H₅.

[0080] The phosphorus element-containing compounds (B2) useful in thepresent invention may also include those compounds having epoxy groupssuch as those compounds described above as compound (A) for examplethose having the following structures:

[0081] wherein R is independently a hydrogen or an alkyl group fromC₁-C₀ such as methyl, ethyl, etc.

[0082] In a most preferred embodiment of the present invention, thephosphorus element-containing monomer (B2) used in the present inventionis for example, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide suchas “Sanko-HCA” commercially available from SANKO of Japan or “StruktolPolydis PD 3710” commercially available from Schill-Seilacher ofGermany;10-(2′,5′-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(such as “Sanko HCA-HQ”); bis(4-hydroxyphenyl)phosphine oxide;tris(2-hydroxyphenyl)phosphine oxide;dimethyl-1-bis(4-hydroxyphenyl)-1-phenylmethylphonate;tris(2-hydroxy-4/5-methylphenyl)phosphine oxide;tris(4-hydroxyphenyl)phosphine oxide,bis(2-hydroxyphenyl)phenylphosphine oxide,bis(2-hydroxyphenyl)phenylphosphinate,tris(2-hydroxy-5-methylphenyl)phosphine oxide; or mixtures thereof.

[0083] Other phosphorus element-containing compounds (B2) which can beused in the present invention, such as isomer mixtures oftris(2-hydroxyphenyl)phosphine oxides, are described in co-pending U.S.Patent Application entitled “Phosphorus Element-Containing CrosslinkingAgents and Flame Retardant Phosphorus Element-Containing Epoxy ResinCompositions Prepared Therewith” Attorney Docket No. 42190, filed ofeven date herewith, incorporated herein by reference.

[0084] The non-halogenated, non-phosphorus element-containing epoxyresin compound (B1) useful in the present invention is preferably acompound which has no alkyl aliphatic substituents or has a low amountof alkyl aliphatic substituents, such as for example the glycidyl etherof a phenol novolac, or the glycidyl ether of bisphenol-F, the glycidylether of bisphenol-S, bisphenol-A, or dihydroxyl ether of fluorene9-bisphenyl; or trisepoxy, or dicyclopentadiene modified phenol epoxyresin, or mixtures thereof.

[0085] The most preferred epoxy resins (B1) are epoxy novolac resins(sometimes referred to as epoxidized novolac resins, a term which isintended to embrace both epoxy phenol novolac resins and epoxy cresolnovolac resins). Such epoxy novolac resin compounds have the followinggeneral chemical structural formula:

[0086] wherein “R” is hydrogen or a C₁-C₃ alkyl, e.g., methyl; and “n”is 0 or an integer from 1 to 10. “n” preferably has an average value offrom 0 to 5. The preferred epoxy novolac resin is when R is preferably ahydrogen in the above Formula II.

[0087] Epoxy novolac resins (including epoxy cresol novolac resins) arereadily commercially available, for example under the trade namesD.E.N.™ (Trademark of The Dow Chemical Company), and Quatrex™ and trisepoxy such as Tactix™ 742 (Trademarks of Ciba). The materials ofcommerce generally comprise mixtures of various species of the aboveformula and a convenient way of characterizing such mixtures is byreference to the average, n′, of the values of n for the variousspecies. Preferred epoxy novolac resins for use in accordance with thepresent invention are those in which n′ has a value of from about 2.05to about 10, more preferably from about 2.5 to about 5.

[0088] In yet another embodiment, the non-halogenated epoxy resinmaterial (I) added to the overall resin composition of the presentinvention may be (C) the reaction product of: (1) a non-halogenatedepoxy resin and (2) a phosphorus element-containing compound capable ofreacting with the epoxy resin (1). The non-halogenated epoxy resin (C1)may be the same as the epoxy resin (A) or (B1) as described above. Thephosphorus element-containing compound (C2) may be the same as thephosphorus compounds (B2) as described above. Examples of the phosphoruselement-containing compounds useful in the present invention alsoinclude the phosphorus compounds described in EP 0806429, incorporatedherein by reference.

[0089] The compositions of the present invention may contain a catalyst(III) capable of promoting the reaction between the multi-functionalphenolic cross-linker and/or the phosphorus element-containing compoundwith the epoxy resin and promoting the curing of the epoxy resin.

[0090] Examples of suitable catalyst materials (III) useful in thepresent invention include for example compounds containing amine,phosphine, ammonium, phosphonium, arsonium or sulfonium moieties.Particularly preferred catalysts are heterocyclic nitrogen-containingcompounds.

[0091] The catalysts (as distinguished from cross-linkers) preferablycontain on average no more than about 1 active hydrogen moiety permolecule. Active hydrogen moieties include hydrogen atoms bonded to anamine group, a phenolic hydroxyl group, or a carboxylic acid group. Forinstance, the amine and phosphine moieties in catalysts are preferablytertiary amine or phosphine moieties; and the ammonium and phosphoniummoieties are preferably quaternary ammonium and phosphonium moieties.

[0092] Among preferred tertiary amines that may be used as catalysts arethose mono- or polyamines having an open-chain or cyclic structure whichhave all of the amine hydrogen replaced by suitable substituents, suchas hydrocarbyl radicals, and preferably aliphatic, cycloaliphatic oraromatic radicals.

[0093] Examples of these amines include, among others,1,8-diazabicyclo(5.4.0) undec-7-en (DBU), methyl diethanol amine,triethylamine, tributylamine, dimethyl benzylamine, triphenylamine,tricyclohexyl amine, pyridine and quinoline. Preferred amines are thetrialkyl, tricycloalkyl and triaryl amines, such as triethylamine,triphenylamine, tri-(2,3-dimethylcyclohexyl)amine, and the alkyldialkanol amines, such as methyl diethanol amines and thetrialkanolamines such as triethanolamine. Weak tertiary arnines, forexample, amines that in aqueous solutions give a pH less than 10 inaqueous solutions of 1 M concentration, are particularly preferred.Especially preferred tertiary amine catalysts are benzyldimethylamineand tris-(dimethylaminomethyl) phenol.

[0094] Examples of suitable heterocyclic nitrogen-containing catalystsinclude those described in U.S. Pat. No. 4,925,901. Preferableheterocyclic secondary and tertiary amines or nitrogen-containingcatalysts which can be employed herein include, for example, imidazoles,benzimidazoles, imidazolidines, imidazolines, oxazoles, pyrroles,thiazoles, pyridines, pyrazines, morpholines, pyridazines, pyrimidines,pyrrolidines, pyrazoles, quinoxalines, quinazolines, phthalozines,quinolines, purines, indazoles, indoles, indolazines, phenazines,phenarsazines, phenothiazines, pyrrolines, indolines, piperidines,piperazines and combinations thereof. Especially preferred are thealkyl-substituted imidazoles; 2,5-chloro-4-ethyl imidazole; andphenyl-substituted imidazoles, and mixtures thereof. Even more preferredare N-methylimidazole; 2-methylimidazole; 2-ethyl-4-methylimidazole;1,2-dimethylimidazole; and 2-methylimidazole. Especially preferred is2-phenylimidazole.

[0095] Preferably, a Lewis acid (IV) is also employed in the compositionof the present invention, especially when the catalyst (III) isparticularly a heterocyclic nitrogen-containing compound.

[0096] Examples of heterocyclic nitrogen-containing catalysts(III),which are preferably used in combination with Lewis acids (IV) are thosedescribed in EP A 526488, EP A 0458502, and GB A 9421405.3, incorporatedherein by reference. The Lewis acids useful in the present inventioninclude for example halides, oxides, hydroxides and alkoxides of zinc,tin, titanium, cobalt, manganese, iron, silicon, aluminum, and boron,for example Lewis acids of boron, and anhydrides of Lewis acids ofboron, for example boric acid, metaboric acid, optionally substitutedboroxines (such as trimethoxyboroxine), optionally substituted oxides ofboron, alkyl borates, boron halides, zinc halides (such as zincchloride) and other Lewis acids that tend to have a relatively weakconjugate base. Preferably the Lewis acid is a Lewis acid of boron, oran anhydride of a Lewis acid of boron, for example boric acid, metaboricacid, an optionally substituted boroxine (such as trimethoxy boroxine,trimethyl boroxine or triethyl boroxine), an optionally substitutedoxide of boron, or an alkyl borate. The most preferred Lewis acid isboric acid. These Lewis acids are very effective in curing epoxy resinswhen combined with the heterocyclic nitrogen-containing compounds,referred to above.

[0097] The Lewis acids and amines can be combined before mixing into theformulation or by mixing with the catalyst in-situ, to make a curingcatalyst combination. The amount of the Lewis acid employed ispreferably at least 0.1 moles of Lewis acid per mole of heterocyclicnitrogen compound, more preferably at least 0.3 moles of Lewis acid permole of heterocyclic nitrogen-containing compound.

[0098] The formulation preferably contains no more than 5 moles of Lewisacid per mole of catalyst, more preferably contains no more than 4 molesof Lewis acid per mole of catalyst and most preferably contains no morethan 3 moles of Lewis acid per mole of catalyst. The total amount of thecatalyst is from about 0.1 wt % to about 3 wt %, based on the totalweight of the composition, preferably from about 0.1 wt % to about 2% wt%.

[0099] The compositions of the present invention may also optionallycontain one or more additional flame retardant additives (V), includingfor example, red phosphorus, encapsulated red phosphorus or liquid orsolid phosphorus-containing compounds, for example, ammoniumpolyphosphate such as “Exolit 700” from Clariant GmbH, a phosphite, orphosphazenes; nitrogen-containing fire retardants and/or synergists, forexample melamines, melem, cyanuric acid, isocyanuric acid andderivatives of those nitrogen-containing compounds; halogenated flameretardants and halogenated epoxy resins (especially brominated epoxyresins); synergistic phosphorus-halogen containing chemicals orcompounds containing salts of organic acids; inorganic metal hydratessuch as Sb₂O₃, Sb₃O₅, aluminum trihydroxide and magnesium hydroxide suchas “Zerogen 30” from Martinswerke GmbH of Germany, and more preferably,an aluminum trihydroxide such as “Martinal TS-610” from MartinswerkeGmbH of Germany; boron-containing compounds; antimony-containingcompounds; and combinations thereof. Examples of suitable additionalflame retardant additives are given in a paper presented at “Flameretardants —101 Basic Dynamics—Past efforts create futureopportunities”, Fire Retardants Chemicals Association, Baltimore Marriotinner harbour hotel, Baltimore Md., Mar. 24-27 1996.

[0100] When additional flame retardants which contain a halogen is usedin the composition of the present invention, the halogen-containingflame retardants are present in amounts such that the total halogencontent in the epoxy resin composition is less than 10 wt %.

[0101] When additional flame retardants which contain phosphorus arepresent in the composition of the present invention, thephosphorus-containing flame retardants are generally present in amountssuch that the total phosphorus content of the epoxy resin composition isfrom about 0.2 wt % to about 5 wt %.

[0102] Also, optionally, other non-flame retardant additives such asinorganic fillers (VI) may be used in the composition of the presentinvention and may include, for example, talc.

[0103] When an inorganic flame retardant, a non-flame retardant or afiller is used in the present invention, the amount of additive orfiller present in the epoxy resin composition of the present inventionis generally form 0 wt % to about 40 wt %; preferably less than 30 wt %and more preferably less than 10 wt %, depending on the end useapplication of the epoxy resin composition.

[0104] The epoxy resin composition of the present invention may alsooptionally contain other additives of a generally conventional typeincluding for example, stabilizers, other organic or inorganicadditives, pigments, wetting agents, flow modifiers, UV light blockers,and fluorescent additives. These additives can be present in amounts offrom 0 to about 5 weight percent, preferably from less than about 3weight percent. Examples of suitable additives are also described inU.S. Pat. No. 5,066,735 and in C.A. Epoxy Resins—Second Ed. at pages506-512 (Mercel Dekker, Inc. 1988).

[0105] Solvents (VIII) may also optionally be used in the composition ofthe present invention. When a solvent is used it may include forexample, propylene glycolmethylether (Dowanol PM™), methoxypropylacetate(Dowanol PMA™), methylethylketone (MEK), acetone, methanol, andcombinations thereof. When a solvent is used in the present invention,the amount of solvent present in the epoxy resin composition of thepresent invention is generally form 0 wt % to about 50 wt %; preferablyfrom about 10 wt % to about 40 wt % and more preferably from about 10 wt% to about 35 wt %, depending on the end use application of the epoxyresin composition.

[0106] Optionally, in some applications it may be desirable to add asmall amount of a halogenated epoxy resin (IX), provided the halogenatedepoxy resin is added in an amount such that the halogen content of theoverall epoxy resin composition of the present invention is less than 10weight percent.

[0107] The compositions of the present invention can be produced bymixing all the components together in any order. Preferably,compositions of the present invention can be produced by preparing afirst composition comprising the epoxy resin, and the second compositioncomprising the multi-functional phenolic hardener. Either the first orthe second composition may also comprise a phosphorus element-containingcompound, a curing catalyst and/or a nitrogen-containingco-cross-linking agent. All other components may be present in the samecomposition, or some may be present in the first, and some in thesecond. The first composition is then mixed with the second composition,and cured to produce a fire retardant epoxy resin.

[0108] The compositions of the present invention can be used to makecomposite materials by techniques well known in the industry such as bypultrusion, moulding, encapsulation, or coating.

[0109] The present invention is particularly useful for making B-stagedprepregs and laminates by well known techniques in the industry.

[0110] A number of preferred embodiments of the present invention areillustrated, in the following specific Examples.

[0111] Examples 1-5 and Comparative Example A

[0112] General production procedure for a polyepoxy and a phosphoruselement-containing compound adduct (Examples 1 and 2)

[0113] In Examples 1 and 2, an epoxy resin (D.E.N.* 438) and aphosphorus element-containing compound (Struktol Polydis PD 3710) wereheated up to 100° C. under nitrogen purge in a 5-liter flange-top glassreactor equipped with an electrically driven mechanical stirrer, air andnitrogen inlets, sample port, condenser and thermocouple. 1000 ppm basedon the total solids of a reaction catalyst triphenylethyl phosphoniumacetate, was added to the reactor and the resulting mixture was heatedto 130-140° C. to initiate the reaction. The reaction temperature wasraised up to at least 160° C. (depending on the size of the reactor) bythe heat of reaction. The reaction mixture was kept at least 165° C. for30 minutes until the theoretical epoxy equivalent weight (EEW=310-330for D.E.N.* 438 and Polydis PD 3710 phosphorus element-containingcompound adduct) was reached. The solid resin was further diluted withmethylethylketone (MEK) and methoxypropylacetate (Dowanol* PMA) (50/50)to a 80 wt % solid solution and cooled to room temperature (H20° C.).

[0114] General production procedure for a polyepoxy and a phosphoruselement-containing compound adduct and a varnish thereof (Example 5)

[0115] In Example 5, D.E.N.* 438 was reacted with Sanko HCA-HQ under thesame conditions as described above for Examples 1 and 2 to reach an EEWof approximately 264. The resultant solid resin was diluted with MEK andDowanol PMA* to a 80 wt % solid. Then, Struktal Polydis PD 3710 andPerstorp 85.36.28 phenol novolac were blended in Dowanol PMA to give a50 wt % solution.

[0116] A resultant adduct useful as a varnish herein was formed bymixing together the above 80 wt % solid solution and the above 50 wt %solution according to the amounts described in Table I.

[0117] General production procedure for a polyepoxy and a phosphoruselement-containing compound blend (Examples 3 and 4)

[0118] In Examples 3 and 4, an epoxy resin (D.E.N.* 438) and aphosphorus element-containing compound (Struktol Polydis PD 3710) wereheated up to 110° C. under nitrogen purge in a 5-liter flange-top glassreactor equipped with an electrically driven mechanical stirrer, air andnitrogen inlets, sample port, condenser and thermocouple. The mixturewas mixed at 110° C. until a homogeneous clear mixture was obtained.Dowanol* PMA and MEK were added to make 80% solid solution and cooled toroom temperature.

[0119] General production procedure for the multi-functional phenolicnovolac hardener solution and the catalyst solution (Examples 1 to 4)

[0120] Perstorp* 85.36.28, a phenolic resin obtained from phenol andformaldehyde having an average Mettler softening point of 103° C., meltviscosity at 150° C.=1.2 Pa.s and a functionality of 4-5, was mixed withDowanol* PMA at room temperature to make a 50% solid solution.

[0121] A catalyst solution was prepared by blending methanol and acatalyst together to form 50 wt. % solution in methanol.

[0122] Boric acid solution was prepared by blending methanol and boricacid together to form 20 wt. % solution in methanol.

[0123] Preparation of varnish, B-staged prepreg, and laminate

[0124] The epoxy resin solution prepared above, the hardener solutionprepared above, the catalyst solution prepared above and optionally aboric acid solution were mixed at room temperature with a mechanicalstirrer for 60 minutes to make a homogeneous mixture. Additionalsolvents (methylethylketone, Dowanol* PM, Dowanol* PMA, acetone ormixtures thereof) were added to adjust the varnish viscosity to 30-50sec. on Ford cup N^(o) 4. The varnishes were aged overnight.

[0125] The varnishes were used to impregnate glass web (style Nr.7628/36 amine silane finish by Porcher SA, France), using a Caratschpilot treater (3 m long). The temperature of the hot air in the oven was160-170° C. The varnish composition, the treater conditions, and theprepreg and laminate performance are summarized in Table I below.

[0126] The prepreg and laminate varnish of Example 4 additionallycontained Martinal TS-610, an aluminum trihydroxide filler material,obtained from Martinswerk GmbH of Germany.

[0127] The IPC test methods employed in the Examples herein are theelectrical laminate industry standard (The Institute For InterconnectionAnd Packaging Electronic Circuits, 3451 Church Street, Evanston, Ill.60203), as follows: Method IPC-Test Method Number: Reactivity (varnish)IPC-TM-650-5.1.410 Rest Geltime @ 170° C., seconds IPC-TM-650-2.3.18 MilFlow, weight percent (wt. %) IPC-TM-650-2.3.17 Tg, ° C.IPC-TM-650-2.4.25 Copper peel strength IPC-TM-650-2.4.8 NMP pick-up Dowmethod C-TS-AA-1012.00 Pressure Cooker Test, wt. % waterIPC-TM-650-2.6.16 pick-up & % passed solder bath @ 260° C. UL94Flammability IPC-TM-650-2.3.10

[0128] TABLE I Formulation compositions, properties, prepreg andlaminate performance. COMPOSITION Comparative (in parts solid by weight)Example 1 Example 2 Example 3 Example 4 Example 5 Example A DEN 438 61.458.5 58.5 53.46 57.9 78 HCA-HQ — — — — 9.44 — PD 3710 17.3 17.5 17.513.77 11.16 22 Phosphorium acetate 0.079 0.076 In-situ blend In-situblend 0.067 0.1 Boric acid 0.79 0.5 0.5 0.5 0.5 0.7 Perstorp phenolicnovolac 21.3 24 24 22.77 21.5 — hardener Dicyandiamide — — — — tc — 22-phenyl imidazole 0.7 0.5 0.5 0.5 0.5 2.1 Aluminum trihydroxide — — —10 — — Additional solvent to achieve MEK/Dowanol MEK/Dowanol MEK/DowanolMEK/Dowanol MEK/Dowanol MEK/ desired velocity PMA/Dowanol PMA/DowanolPMA/Dowanol PMA/Dowanol PMA/Dowanol Dowanol PM PM PM PM PM PM VARNISHCHARACTERISTICS Viscosity 45 36 35 6 39 37 (Ford cup #4) (seconds)Reactivity, 170 158 160 168 112 255 Geltime @ 170° C. (seconds) Treatercondition Oven 172 172 173 173 169 183 temperature (° C.) Winding speed,1.3 1.5 1.0 1.6 1.5 0.88 (meter/minute) PREPREG CHARACTERISTICS Resincontent (wt %) 47 48 46 43 45 46 Rest Geltime @ 170° C. (seconds) 59 7560 48 42 99 Mil Flow (wt %) 27 32 22 20 23 25 Minimum melt viscosity 10755 30 31 52 112 measured @ 140° C. (Pa · s) LAMINATE 1.5 hour @ 1.5 hour@ 1.5 hour @ 1.5 hour @ 1.5 hour @ 1.5 hour @ PERFORMANCE 190° C. 190°C. 190° C. 190° C. 190° C. 190° C. Laminate thickness (MM) 1.50-1.591.67-1.81 1.72-1.86 1.40-1.46 1.59-1.63 1.40-1.68 Tg1/2 (° C.) 129/136126/133 136/140 132/137 140/143 131/133 Press Cooker Test, wt % waterpick-up/% passed solder bath @ 260° C. 40 minutes n.m.* n.m. n.m. n.m.0.33/100  0.62/100  60 minutes 0.43/100  0.40/100  n.d. 0.37/100 0.35/75   0.73/0   75 minutes n.m. 0.44/50   0.43/100  n.m. n.m. n.m. 90minutes 0.54/25   n.m.  0.5/100 0.44/50   n.m. n.m. Total burning time(seconds) 46 46 27 39 46 40 UL94 V-0 V-0 V-0 V-O V-O V-0

[0129] The above results show that the phenolic cure laminate systems ofExamples 1-5 exhibit much higher moisture resistance (lower water pickup at longer resistance time) than the dicyandiamide cured system ofComparative Example A.

[0130] Examples 6-9

[0131] Examples 6, 7, 8 and 9, shown in Table II below, were preparedaccording to the “General production procedure for a polyepoxy and aphosphorus element-containing compound adduct” described above,particularly as described according to Example 5. The properties of theresultant adduct are shown in Table II. TABLE II COMPONENT Example 6Example 7 Example 8 Example 9 D.E.N. 438 (wt %) 64.5 D.E.R. 330 (wt %)75 D.E.R. 354LV 70 (wt %) D.E.N. 431 (wt %) 75 HCA-HQ (wt %) 10.5 25 3025 Triphenylethylphospho- 1000 1000 1000 1000 nium acetate catalyst,(ppm) PROPERTIES EEW 264 395 451 378 Melt viscosity @ 1.2 0.76 0.88 1.6150° C., (Pa · s)

[0132] HCA-HQ has very poor solubility in organic solvents and in epoxyresins below 120° C. and it is very difficult to use HCA-HQ without anypre-reaction with an epoxy resin. However, HCA-HQ has high thermalresistance (Tg>130° C.) and has good flame retardancy for curedpolymers. HCA-HQ has a 2 phenolic functionality and is useful as a chainextender to increase the molecular weight of epoxy resins. Examples 6 to9 show that it is possible to increase the molecular weight and meltviscosity of liquid epoxy resins to an appropriate value such as from0.4 to 1.2 Pa·s at 150° C.

[0133] The resin of Example 8 above was made into a varnish compositionby blending the resin with a curing agent, a dicydiamide (2 phr), boricacid (0.7 phr) and a catalyst, 2-phenyl imidazole (1.4 phr) in asolvent, Dowanol PMA*. The varnish had a reactivity, geltime at 170° C.,of 200 seconds; and a Tg of 135° C. The varnish was cured at 190° C. for90 minutes.

What is claimed is:
 1. A flame retardant phosphorus element-containingepoxy resin composition substantially free of halogen, comprising: (I) anon-halogenated epoxy resin material selected from: (A) anon-halogenated, phosphorus element-containing epoxy resin; (B) amixture of: (1) a non-halogenated, non-phosphorus element-containingepoxy resin, and (2) a phosphorus element-containing compound; (C) thereaction product of: (1) a non-halogenated epoxy resin; and (2) aphosphorus element-containing compound; or (D) a combination of two ormore of Components (A) to (C); and (II) (A) a multi-functional phenoliccrosslinking agent having a hydroxy functionality of at least 2; (B) amaterial which forms a multi-functional phenolic crosslinking agenthaving a hydroxy functionality of at least 2 upon heating; or (C) amixture of components (A) and (B).
 2. The composition of claim 1 whereinthe multi-functional phenolic cross-linking agent is present in anamount of from about 50% to about 150% of the stoichiometric amountneeded to cure the epoxy resin.
 3. The composition of claim 1 whereinthe phosphorus element-containing compound contains functionalityselected from an epoxy, a phosphine, a hydroxy, an anhydride, an amineor an acid functionality.
 4. The composition of claim 1 wherein theamount of the non-halogenated epoxy resin material based on solids isfrom about 30 to about 95 weight percent, of the composition.
 5. Thecomposition of claim 2 wherein the phosphorus element-containingcompound is present in an amount sufficient to provide from about 0.2weight percent to about 3.5 weight percent phosphorus in the curingcomposition.
 6. The composition of claim 1 including: (III) a catalystcapable of promoting the reaction of the phenolic/hydroxy group of themulti-functional phenolic crosslinking agent with the epoxy group of theepoxy resin material.
 7. The composition of claim 6 wherein the catalystis present in an amount of from about 0.1 weight percent to about 3weight percent.
 8. The composition of claim 6 including: (IV) a Lewisacid.
 9. The composition of claim 8 wherein the Lewis acid is present inan amount of up to about 4 moles per mole of catalyst.
 10. Thecomposition of claim 6 wherein the catalyst is an amine catalystcompound.
 11. The composition of claim 10 wherein the catalyst is aheterocyclic nitrogen-containing compound.
 12. The composition of claim10 wherein the catalyst is selected from the group comprising2-phenylimidazole; 2-methylimidazole; 2-ethyl,4-methylimidazole andimidazole.
 13. The composition of claim 8 wherein the Lewis acid is aboron-containing compound.
 14. The composition of claim 13 wherein theLewis acid is selected from the group comprising boric acid, metaboricacid, boroxines and alkyl borates.
 15. The composition of claim 1including (V) a flame-retardant additive.
 16. The composition of claim15 wherein the flame-retardant additive (V) is selected from aluminiumtrihydroxide, magnesium hydroxide, red phosphorus, encapsulated redphosphorus, ammonium polyphosphate and mixtures thereof.
 17. Thecomposition of claim 15 wherein the flame-retardant additive (V) is ahalogenated bisphenol A in an amount less than 10 weight percent. 18.The composition of claim 17 wherein the flame retardant (V) istetrabromobisphenol A.
 19. The composition of claim 6 including: (VI) afiller material.
 20. The composition of claim 19 wherein the filler (VI)is an inorganic filler material.
 21. The composition of claim 1including: (VII) a multi-functional co-crosslinking agent different fromthe multi-functional phenolic crosslinking agent (II).
 22. Thecomposition of claim 21 wherein the multi-functional co-crosslinkingagent (VII) is selected from an anhydride, a nitrogen-containingcrosslinking agent having an amine functionality of at least 2 and astyrene maleic anhydride copolymer.
 23. The composition of claim 22wherein the co-cross-linking agent (VII) is present in an amount of from0 to about 40% of the stoichiometric amount needed to cure the epoxyresin.
 24. The composition of claim 1 wherein the phosphoruselement-containing epoxy resin (A) is obtained by epoxidizing aphosphorus-containing compound.
 25. The composition of claim 1 whereinthe phosphorus element-containing epoxy resin (A) is obtained byreacting an epoxy resin with a phosphorus element-containing compoundcapable of reacting with the epoxy resin.
 26. The composition of claim 1wherein the epoxy resin (B1) or (C1) is an epoxy-polyisocyanatecopolymer.
 27. The composition of claim 26 wherein the isocyanate isMDI, TDI or isomers thereof.
 28. The composition of claim 1 including:(VIII) a solvent.
 29. The composition of claim 1 including: (IX) ahalogenated epoxy resin compound in an amount such that the halogencontent in the epoxy resin composition is less than 10 weight percent.30. The composition of claim 1 wherein the epoxy resin is an epoxynovolac, an epoxy of tris(hydroxyphenyl)methane, a cresol epoxy novolac,a dicyclopentadiene modified epoxy novolac, glycidyl of tetraphenolethane or mixtures thereof.
 31. The composition of claim 1 wherein thephosphorus element-containing compound is9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide;10-(2′,5′-dihydroxyphenyl)-9, 10-dihydro-9-oxa-10-phoxphaphenanthrene-10-oxide; bis(4-hydroxyphenyl)phosphine oxide; tris(2-hydroxyphenyl)phosphine oxide; dimethyl- 1-bis(4-hydroxyphenyl)-1-phenylnethylphonate; tris(2-hydroxy-4/5-methylphenyl)phosphine oxide;dimethyl phosphite; vinyl phosponic acid; tris(4-hydroxyphenyl)phosphineoxide, bis (2-hydroxyphenyl)phenylphosphine oxide,bis(2-hydroxyphenyl)phenylphosphinate,tris(2-hydroxy-5-methylphenyl)phosphine oxide; or mixtures thereof. 32.The composition of claim 1 wherein the multi-functional phenoliccrosslinking agent is 2 to 10 functional phenol novolac.
 33. Thecomposition of claim 1 wherein the phosphorus-containing epoxy resin isa reaction product of: (i) epoxy novolac, epoxy oftris(hydroxyphenyl)methane, dicyclopentadiene modified phenol epoxynovolac, or glycidyl of tetraphenol ethane and (ii)9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.
 34. The compositionof claim 1 wherein the phosphorus element-containing epoxy resin is areaction product of: (i) an epoxy novolac, epoxy oftris(hydroxyphenyl)methane, dicyclopentadiene modified phenol epoxynovolac, glycidyl of tetraphenol ethane, diglycidyl ether ofbisphenol-A, or diglycidyl ether of bisphenol-F, and (ii) a phosphoruselement-containing compound selected from10-(2′,5′-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, bis(4-hydroxyphenyl)phosphine oxide; tris(2-hydroxyphenyl)phosphine oxide; dimethyl-1-bis(4-hydroxyphenyl)-1-phenylmethylphonate;tris(2-hydroxy-4/5-methylphenyl)phosphine oxide; dimethyl phosphite;vinyl phosphonic acid; tris(4-hydroxyphenyl)phosphine oxide,bis(2-hydroxyphenyl)phenylphosphine oxide,bis(2-hydroxyphenyl)phenylphosphinate, tris(2-hydroxy-5-methylphenyl)phosphine oxide; or mixtures thereof.
 35. The compositionof claim 1 wherein the multi-functional phenolic crosslinking agent isselected from phenolic resins obtained from phenols or alkyl phenols andformaldehyde; tris(hydroxyphenol) mehtane; dicyclopentadiene phenolnovolac; tetraphenol ethane; or mixtures thereof.
 36. The composition ofclaim 1 wherein Component II(B) is a benzoxazine based material.
 37. Thecomposition of claim 36 wherein Component II(B) is selected frombenzoxazine of phenol phthalein, benzoxazine of bisphenol-A, benzoxazineof bisphenol-F, benzoxazine of phenol novolac, and mixtures thereof. 38.The composition of claim 1 which provides a fire material classificationof V-O based on UL94 (vertical test).
 39. A “B-stage” material made fromthe composition of claim
 1. 40. A laminate made from the composition ofclaim
 1. 41. A process for making a flame retardant phosphoruselement-containing epoxy resin composition substantially free of halogencomprising the step of mixing: (1) a non-halogenated epoxy resinmaterial selected from: (A) a non-halogenated, phosphoruselement-containing epoxy resin; (B) a mixture of: (1) a non-halogenated,non-phosphorus element-containing epoxy resin, and (2) a phosphoruselement-containing compound; (C) the reaction product of: (1) anon-halogenated epoxy resin; and (2) a phosphorus element-containingcompound; or (D) a combination of two or more of components (A) to (C);and (II) (A) a multi-functional phenolic crosslinking agent having ahydroxy functionality of at least 2; (B) a material which forms amulti-functional phenolic crosslinking agent having a hydroxyfunctionality of at least 2 upon heating; or (C) a mixture of components(A) and (B).
 42. A flame retardant hardener composition substantiallyfree of halogen capable of being added to an epoxy resin, comprising:(i) a phosphorus element-containing compound; and (ii) (a) amulti-functional phenolic crosslinking agent having a hydroxyfunctionality of at least 2; (b) a material which forms amulti-functional phenolic crosslinking agent having a hydroxyfunctionality of at least 2 upon heating; or (c) a mixture of components(a) and (b).
 43. The composition of claim 42 including a Lewis acidinhibitor.
 44. A phosphorus element-containing epoxy resin adductcomprising the reaction product of (1) a non-halogenated epoxy resin;and (2) a phosphorus element-containing compound.
 45. The adduct ofclaim 44 wherein the phosphorus element-containing compound is 10-(2′,5′-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phoxphaphenanthrene-10-oxide.